How do I create an equilateral tetrahedron?
Use the the AddMesh: Extra Objects plugin (to access the user preferences use ctrlaltu):

Now you have to add Mesh-Math Function-Regular Solid

And select Source:Tetrahedron.


For older versions of Blender:
In user preferences  go to &quot;Addons&quot; and enable &quot;Add Mesh:Regular Solids&quot;.

And select platonic solids when pressing shifta